Wednesday, January 11, 2006

Changes are for REAL

In my January 7 posting, I discussed recent behaviors (please review, if needed) that could lead to circulation change, to that as depicted by Stage 1 of our Synoptic-Dynamic Model of subseasonal variability (SDM). This stage favors troughs coming into western North America. Indeed, that circulation change is occurring, only to mature during the next couple of weeks. As a quick review, factors leading to this change include robust tropical convection across the Indian Ocean (not a MJO), and lowering pressures/heights across the polar latitudes. The impacts from Stratospheric-Tropospheric interactions over the Arctic in regard to making any week 1-2 predictions are definitely unclear for our current situation. Intense tropical thunderstorm activity across the south Pacific is contributing to STJ activity across the east Pacific, which may also be important for future western USA troughs/storms.

I continue to like the general scenario given by the CDC and NCEP ensembles (other models are getting on the same general path). One storm looks likely across the Rockies and Plains during about the Sunday-Wednesday period (January 15-18). This system looks to bring heavy precipitation first across much of the west coast, heavy snow across the Rockies, and perhaps intense thunderstorms over the south central and southeast states.

Based on monitoring, I think there may be a more significant trough along the west coast during much of week 2 (January 18-25). That latter would be part of a trough-ridge-trough pattern across the PNA sector. Beyond stating the above, details are unclear. Probilistically, perhaps 2-3 synoptic systems would first impact particularly California, and then move through the Rockies and subsequently turn northeast through the central part of the country. High impact weather concerns from this option include heavy cold sector snowfall and severe thunderstorms in the warm air. While some Arctic air would likely bleed southward into the northern Rockies along with colder than normal temperatures across much of the west, the eastern states should experience above average temperatures. Whatever the case, we need to monitor!!!

For southwest Kansas, I continue to express the concerns about systems being too progressive, etc., as I did on January 7. HOWEVER, I am definitely encouraged about opportunities for precipitation starting with the Monday storm. Even though the most significant precipitation will likely be off to the east and north, a period of some measurable snowfall with lots of wind needs to be a concern. Temperatures should then warm rapidly to above normal levels (along with dry) by the middle to late part of next week. By next weekend (January 21-22), that trend may change tremendously. PROBABILISTICALLY, our circulation state may allow for closed/slow moving lows to develop across the southwest states by that time. That would allow for more time to get moisture transport from both the Gulf of Mexico and eastern Pacific STJs, with subsequent increased precipitation chances.